92377cf71a
* Edited wording in a test * Rearranged the tests Co-authored-by: Oliver Eyton-Williams <ojeytonwilliams@gmail.com>
98 lines
2.4 KiB
Markdown
98 lines
2.4 KiB
Markdown
---
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id: 5900f36e1000cf542c50fe81
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challengeType: 5
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isHidden: false
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title: 'Problem 2: Even Fibonacci Numbers'
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forumTopicId: 301838
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---
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## Description
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<section id='description'>
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Each new term in the Fibonacci sequence is generated by adding the previous two terms. By starting with 1 and 2, the first 10 terms will be:
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<div style='text-align: center;'>1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...</div>
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By considering the terms in the Fibonacci sequence whose values do not exceed <code>n</code>, find the sum of the even-valued terms.
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</section>
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## Instructions
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<section id='instructions'>
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</section>
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## Tests
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<section id='tests'>
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```yml
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tests:
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- text: <code>fiboEvenSum(10)</code> should return a number.
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testString: assert(typeof fiboEvenSum(10) === 'number');
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- text: Your function should return an <code>even</code> value.
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testString: assert.equal(fiboEvenSum(10) % 2 === 0, true);
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- text: 'Your function should sum the even-valued Fibonacci numbers: <code>fiboEvenSum(8)</code> should return 10.'
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testString: assert.strictEqual(fiboEvenSum(8), 10);
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- text: <code>fiboEvenSum(10)</code> should return 10.
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testString: assert.strictEqual(fiboEvenSum(10), 10);
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- text: <code>fiboEvenSum(34)</code> should return 44.
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testString: assert.strictEqual(fiboEvenSum(34), 44);
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- text: <code>fiboEvenSum(60)</code> should return 44.
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testString: assert.strictEqual(fiboEvenSum(60), 44);
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- text: <code>fiboEvenSum(1000)</code> should return 798.
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testString: assert.strictEqual(fiboEvenSum(1000), 798);
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- text: <code>fiboEvenSum(100000)</code> should return 60696.
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testString: assert.strictEqual(fiboEvenSum(100000), 60696);
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- text: <code>fiboEvenSum(4000000)</code> should return 4613732.
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testString: assert.strictEqual(fiboEvenSum(4000000), 4613732);
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```
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</section>
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## Challenge Seed
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<section id='challengeSeed'>
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<div id='js-seed'>
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```js
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function fiboEvenSum(n) {
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// You can do it!
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return true;
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}
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fiboEvenSum(10);
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```
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</div>
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</section>
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## Solution
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<section id='solution'>
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```js
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const fiboEvenSum = (number) => {
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if (number <= 1) {
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return 0;
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} else {
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let evenSum = 0,
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prevFibNum = 1,
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fibNum = 2; // According to problem description our Fibonacci series starts with 1, 2
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for (let i = 2; fibNum <= number; i++) {
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if (fibNum % 2 == 0) {
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evenSum += fibNum;
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}
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[prevFibNum, fibNum] = [fibNum, prevFibNum + fibNum];
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}
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return evenSum;
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}
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};
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```
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</section>
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